This invention relates to roofing panels for accepting inclined solar panels thereon, and to an associated method for installing solar panels on a roof.
One type of roofing used on many large buildings is a protected membrane roofing system. In the PMR system, an insulation layer is situated above a roofing membrane, for protecting the membrane. Any rain water that passes through the insulation layer will flow over the membrane below for removal through drainage points. Such a system is commonly used on flat roofs of large buildings.
From a conservation and environmental perspective, it would be an advantage for more buildings to use solar panels to generate electric power, particularly those with large roof surface area. One barrier to such use is the high cost of labor and materials for installing a new roof with associated solar panels. With the development of new solar cell technology, it has been found that the non-solar cell components necessary for installing and utilizing a photovoltaic system, particularly the roof itself, become the critical factor which dominates the decision as to whether or not to use a solar system. This is particularly true with older building where substantial roofing modifications cannot be cost justified.
A commonly used technique for installing inclined solar panels on roofs uses gravel-filled ballast trays for anchoring the panels to the roof surface. The ballast trays must have considerable weight to perform their designated function of holding the inclined panels down at design wind loads. This weight, of course, places substantial stress on the roof and the roof supports, and the ballast required adds substantially to the cost of installation.
One method for installing solar panels on roofs, disclosed in U.S. Pat. No. 5,316,592 to Dinwoodie, involves shop assembling thermal insulation blocks directly to the bottom surfaces of photovoltaic modules to produce two-layer integral units and disposing the two layer units as a layer on top of an installed roofing membrane.
In U.S. Pat. No. 4,886,554 to Woodring et al., a photovoltaic cell and a tapered insulation block are respectively bonded to upper and lower surfaces of a paver to produce a three-layer paver unit which in turn is installed in a layer over a roofing membrane.
In both these methods, to obtain even a slight angle between the photovoltaic modules and a roof surface, the insulation blocks must be manufactured with that angle between their upper and lower sides. While such systems do not require ballast, they also do not provide an optimum angle for maximizing the efficiency of the solar panels. Additionally, there is no simple way to remove the integral solar panel for replacement or repair without disassembling the roof and exposing the underlying roof membrane. Further, the solar panel must be mounted when the insulation is installed, and does not provide for later adding a solar panel after the roof is installed. Finally, the integral insulation blocks remain costly to manufacture, since the photovoltaic modules must be mounted directly on an insulation block or to a paver. Transportation and installation of the roof components is more difficult since the photovoltaic modules are delicate, and are more likely to be damaged during roof construction.